The broad goal of this project is to examine the neuroendocrine and gonadal regulation of FSH in the female. These studies will define the relative contributions of inhibins A & B to the control of FSH secretion and folliculogenesis during the normal menstrual cycle using correlation of daily FSH and inhibin A & B levels, estradiol and follicular size across the menstrual cycle. Populations will consist of both younger (age 18-34) and older (age 35-45) cycling women and in infertile women with high FSH levels.